1. Field of the Invention
The present invention relates to an object (a product including a machine, a manufacture, and a composition of matter) and a method (a process including a simple method and a production method). In particular, one embodiment of the present invention relates to a semiconductor device, a light-emitting device, a power storage device, a driving method thereof, or a manufacturing method thereof.
In this specification, a semiconductor device refers to all the devices that can operate by utilizing semiconductor characteristics. An electrooptic device, a semiconductor circuit, and an electronic device may be included in the category of semiconductor devices or alternatively may include semiconductor devices in their categories.
2. Description of the Related Art
A technique by which transistors are formed using semiconductor thin films formed over a substrate having an insulating surface has been attracting attention. These transistors are applied to a wide range of electronic devices such as an integrated circuit (IC) or an image display device (also simply referred to as a display device). Although a silicon-based semiconductor material is widely known as a material of a semiconductor thin film applicable to a transistor, as another material, a semiconductor material using an oxide has been attracting attention.
For example, a transistor including an oxide (oxide semiconductor) containing indium (In), gallium (Ga), and zinc (Zn) is disclosed (see Patent Document 1).
Further, Patent Document 2 discloses that oxygen is released from an oxide semiconductor during a manufacturing process of a semiconductor device including an oxide semiconductor and thus oxygen vacancies are formed.